Ions are used in a plurality of semiconductor processes, such as implantation, amorphization, deposition and etching processes. These ions may be created within an ion source chamber and extracted through an extraction aperture in the ion source chamber.
In certain embodiments, the ion source comprises an indirectly heated cathode. A filament is disposed behind the cathode and energized to emit thermionic electrons. These electrons then strike the back surface of the cathode, causing the cathode to increase in temperature and emit electrons into the ion source chamber. These energized electrons collide with a feed gas in the ion source chamber to create ions, which can be extracted through an extraction aperture in the ion source.
In some embodiments, the extraction aperture is in the shape of an elongated slit, having a length that is much greater than its height. The ions are extracted through this extraction aperture in the form of a ribbon ion beam. One parameter that is monitored in ion implanters is ion beam uniformity. This term refers to the consistency of beam current across the entire length of the ribbon ion beam. Components that are located downstream from the ion source may be utilized to compensate for any non-uniformity in the ribbon ion beam extracted from the ion source. However, these components tend to reduce the overall beam current and may cause the ion beam to lose some amount of parallelism.
Thus, it would be beneficial if there were an apparatus that allowed improved control over the ion beam that is extracted from the ion source. Further, it would be advantageous if there were a method to control that apparatus which allowed the ribbon ion beam to be tuned without sacrificing beam current and parallelism.